I still haven't seen anyone give an answer to gerontocrat's question about whether we're witnessing a bigger change in the last few years, to bring cause this decline in Antarctic sea ice extent, or whether this is just an anomaly. The rate of melt occurring now may seems like an important piece of evidence to be considered.

I tried to hint to the recovered Nimbus missions above when you asked the first time about losses in previous decades wdmn:

Regarding my comments above in #40 & #51 around the recovered Nimbus missions, I'll quote the cires article in #40 to highlight what I personally think is the thing to look for within a couple of years. A record low.

Quote

“And the Antarctic blew us away,” he said. In 1964, sea ice extent in the Antarctic was the largest ever recorded, according to Nimbus image analysis. Two years later, there was a record low for sea ice in the Antarctic, and in 1969 Nimbus imagery, sea ice appears to have reached its maximum extent earliest on record.

Thanks Sleepy, I'm asking too many questions and not paying enough attention to the answers. This is a great resource. I notice that gerontocrat's temperature graphs have massive +ive and -ive anomalies for the years mentioned as being record max and min extents. I'm still new to all of this, and it's fascinating to see how different antarctica's response to the global energy imbalance has been.

Thanks for those links Sleepy., especially the forecasts.It will be interesting to compare the reality with those forecasts next Feb/March.

Mind you, in my simple mind, two years data showing a marked change is just 2 data points, three years only may be a start of a trend.

Meanwhile, daily data update.

JAXA ANTARCTIC Sea Ice Extent - 10,408,184 km2（December 12, 2018）

A lower drop of 224k , just 14k greater than average on this day.

Extent is 3rd lowest, though still 1.64 million km2 greater than 2016 on this day, but only 77k above 2017. Extent loss from maximum is 275k (3.7%) greater than average so far, with on average 47% of extent loss for the season done and just 69 days to minimum (compared wiith last 10 years average).

A record low minimum (of below 2 million km2) is a real possibility, making 3 years in a row. So much for increased Antarctic Ice Sheet melt causing increased sea ice extent.

Extent is 3rd lowest, though still 1.61 million km2 greater than 2016 on this day, but only 56k above 2017. Extent loss from maximum is 337k (4.4%) greater than average so far, with on average 48% of extent loss for the season done and just 68 days to minimum (compared wiith last 10 years average).

A record low minimum (of below 2 million km2) is a real possibility, making 3 years in a row. So much for increased Antarctic Ice Sheet melt causing increased sea ice extent.

Antarctic compaction is still going down, now over 10% below average. If we could rearrange the ice in a way for it to be at average compaction then extent would be one million km2 lower. That's equal to 5 days of average losses without any actual melt.

Antarctic compaction is still going down, now over 10% below average. If we could rearrange the ice in a way for it to be at average compaction then extent would be one million km2 lower. That's equal to 5 days of average losses without any actual melt.

How many SDs out of "normal" now ?

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"Para a Causa do Povo a Luta Continua!""And that's all I'm going to say about that". Forrest Gump"Damn, I wanted to see what happened next" (Epitaph)

Antarctic compaction is still going down, now over 10% below average. If we could rearrange the ice in a way for it to be at average compaction then extent would be one million km2 lower. That's equal to 5 days of average losses without any actual melt.

Extent is 2nd lowest, though still 1.54 million km2 greater than 2016 on this day, and just 25 k below 2017. Extent loss from maximum is 463k (5.9%) greater than average so far, with on average 49% of extent loss for the season done and just 67 days to minimum (compared wiith last 10 years average).

A record low minimum (of well below 2 million km2) is a real possibility, making 3 years in a row. So much for increased Antarctic Ice Sheet melt causing increased sea ice extent.

Being at the beginning of the Austral summer, low extent and area means once again with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Extent is 2nd lowest, though still 1.50 million km2 greater than 2016 on this day, and just 12 k below 2017. Extent loss from maximum is 519k (6.4%) greater than average so far, with on average 50.6% of extent loss for the season done and just 66 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. So much for increased Antarctic Ice Sheet melt causing increased sea ice extent.

Being at the beginning of the Austral summer, low extent and area means once again with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Extent loss of 428k , 181k greater than average on this day. This is unusual, though in 2011 there were two days in a row of 400K+ extent losses, at exactly this time of year.

Extent is 2nd lowest, though still 1.167 million km2 greater than 2016 on this day, but 222 k below 2017. Extent loss from maximum is 744k (8.7%) greater than average so far, with on average 53.5% of extent loss for the season done and just 64 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. So much for increased Antarctic Ice Sheet melt causing increased sea ice extent.

Most of the remaining ice is at low concentration, so being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Antarctic Sea Ice Area is now at record low, 60,000 km2 below 2016 and 2.72 SD below the mean. This is even slightly below the low estimate of my SIPN_south forecast which is already far lower than any other forecast. With compaction staying at record low too, I don't expect this year to slow down in area losses like 2016 which turned to above average compaction at this point.

Extent is 2nd lowest, though still at 9a reducing) 1.02 million km2 greater than 2016 on this day, but 336 k below 2017. Extent loss from maximum is 808k (9.2%) greater than average so far, with on average 55.1% of extent loss for the season done and 63 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. Indeed, the average remaining melt from this day to minimum would produce a minimum of 1.4 million km2, 0.75 million km2 less than the record low in 2016-17. This result is hard to believe.

Most of the remaining ice is at low concentration, so being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

I did not go back as far as 1979. As the year turned, that 1979 2nd lowest turned into the middle of the pack by end of January 1980.

It is also true that Antarctic sea ice extent did not decrease, and maybe increased a fraction until about 2014. The question is whether the last three years' large decreases are temporary or permanent.

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"Para a Causa do Povo a Luta Continua!""And that's all I'm going to say about that". Forrest Gump"Damn, I wanted to see what happened next" (Epitaph)

Shared Humanity

The attached image shows the extent to which 2018 sea ice is falling to bits compared with 2016

The Ross Sea especially concerns me. I am not sure the exact year but, recently, there was an unprecedented melt on the surface of the Ross Ice Shelf. Could the destruction of the ice in the Ross Sea set us up for a repeat?

Extent is 2nd lowest, though still at (a reducing) 0.97 million km2 greater than 2016 on this day, but 414 k below 2017. Extent loss from maximum is 896k (10.0%) greater than average so far, with on average 56.2% of extent loss for the season done and 62 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. Indeed, the average remaining melt from this day to minimum would produce a minimum of 1.31 million km2, 0.83 million km2 less than the record low in 2016-17. This result is hard to believe.

All models have limitations. The first table attached shows that remaining melt in two previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Most of the remaining ice is at low concentration, so being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

If austral summer sea ice went to zero this year, how significant/unexpected would that be? I understand that most of the ice disappears each year anyway, but it would still be quite an increase in AWP, I would guess; would it effect glacial melt at all?

If austral summer sea ice went to zero this year, how significant/unexpected would that be? I understand that most of the ice disappears each year anyway, but it would still be quite an increase in AWP, I would guess; would it effect glacial melt at all?

We won't get to truly zero ice, because the Weddel Sea is sheltered by the Antarctic Peninsula. It will be about as hard to melt as the ice pack north of Greenland/Canadian Archipelago. In the 40 years of satellite observations there has only been one year 1992/1993 which had exceptional weather to force melt in this region. Due to this event 1993 still holds the record low in sea ice area with 1.248 million km2 compared to second place 2017 with 1.514. Without significant melt in the west Weddel Sea we won't reach record low sea ice area this year either.

If austral summer sea ice went to zero this year, how significant/unexpected would that be? I understand that most of the ice disappears each year anyway, but it would still be quite an increase in AWP, I would guess; would it effect glacial melt at all?

We won't get to truly zero ice, because the Weddel Sea is sheltered by the Antarctic Peninsula. It will be about as hard to melt as the ice pack north of Greenland/Canadian Archipelago. In the 40 years of satellite observations there has only been one year 1992/1993 which had exceptional weather to force melt in this region. Due to this event 1993 still holds the record low in sea ice area with 1.248 million km2 compared to second place 2017 with 1.514. Without significant melt in the west Weddel Sea we won't reach record low sea ice area this year either.

If austral summer sea ice went to zero this year.... it would still be quite an increase in AWP, I would guess. would it effect glacial melt at all?

AWP? Not really. as it would happen late February / March, at the end of the Austral summer, so insolation is already dropping quickly by then. It is what is happening now that is really shoving additional heat into the southern ocean. First image shows how daily Albedo Warming Potential is going through the roof. Tealight might have to increase the range on the y-axis.

Glacial melt. The longer the ice shelves are exposed to the open ocean the longer the impact of wave action and surface currents. And surface air will have lost less heat from passing over sea ice. How significant ? not a clue.

2nd image shows how broken up most of the remaining sea ice is. The sea ice in the Ross Sea is toast. Final sea ice area and extent will be determined by how resistant the purple bits will be to melting.

ps:-Note how Iceberg A-68 is right in the middle of the most stubborn sea ice (orange circle).

Just a stupid question: What is counted as Antarctic Sea Ice?1. We have a lot of thin floes of sea ice (mostly 1-year ice), some of them packed together by winds or currents, but principally mobile2. We have fast ice around the coast of the continent and between the coastline and the little islands around Antarctica, some of it grounded to submarine hills3. We have large broken-off ice bergs (originating from shelves or fast ice), some of them dozens of km² large, floating around and slowly melting4. We have ice shelves (like Ross, Rønne/Filchner, Getz, Larsen) etc.The latter one do probably not count into "Antarctic Sea Ice", even thogh there is water beneath them. What is with fast ice?

I notice that sea ice concentration in the Weddel Sea is already lower on the north and western edges than in the image of the lowest possible area that you posted.

@gerontocrat

I have been looking at tealight's graphs and saw the recent spike. But looking ahead to the March low 1993 still had a higher AWP than any year, so low does make some difference. I'm just trying to imagine where that low point might be and so what the slope from the solstice until then will be like. I guess I should do some calculations to see how much of a difference it might make.

Just a stupid question: What is counted as Antarctic Sea Ice?1. We have a lot of thin floes of sea ice (mostly 1-year ice), some of them packed together by winds or currents, but principally mobile2. We have fast ice around the coast of the continent and between the coastline and the little islands around Antarctica, some of it grounded to submarine hills3. We have large broken-off ice bergs (originating from shelves or fast ice), some of them dozens of km² large, floating around and slowly melting4. We have ice shelves (like Ross, Rønne/Filchner, Getz, Larsen) etc.The latter one do probably not count into "Antarctic Sea Ice", even thogh there is water beneath them. What is with fast ice?

So, in theory,- if the origin of the ice is the sea, it is sea ice,- if the origin of the ice is from land / snow, it is not sea ice.

In practice, 1. and 2. are sea ice.3. , the bergs, even though they are mostly frozen freshwater, are included as how can the satellites cope with hundreds, thousands, of moving objects? I wonder if berg A-68 (5,000 km2) is masked out? But with sea ice in the range from 2 to 20 million, and daily ice loss of around 200,000 or more per day at the moment, it is not significant.4. The ice shelves are frozen freshwater formed from glaciers moving into the ocean plus a few 10s of thousands of years of snowfall on top. I wonder if some have sea ice at their base from when they first formed?

Both NSIDC and JAXA use a mask to exclude the continent and the ice shelves from the measurements.

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"Para a Causa do Povo a Luta Continua!""And that's all I'm going to say about that". Forrest Gump"Damn, I wanted to see what happened next" (Epitaph)

Just a stupid question: What is counted as Antarctic Sea Ice?1. We have a lot of thin floes of sea ice (mostly 1-year ice), some of them packed together by winds or currents, but principally mobile2. We have fast ice around the coast of the continent and between the coastline and the little islands around Antarctica, some of it grounded to submarine hills3. We have large broken-off ice bergs (originating from shelves or fast ice), some of them dozens of km² large, floating around and slowly melting4. We have ice shelves (like Ross, Rønne/Filchner, Getz, Larsen) etc.The latter one do probably not count into "Antarctic Sea Ice", even thogh there is water beneath them. What is with fast ice?

So, in theory,- if the origin of the ice is the sea, it is sea ice,- if the origin of the ice is from land / snow, it is not sea ice.

In practice, 1. and 2. are sea ice.3. , the bergs, even though they are mostly frozen freshwater, are included as how can the satellites cope with hundreds, thousands, of moving objects? I wonder if berg A-68 (5,000 km2) is masked out? But with sea ice in the range from 2 to 20 million, and daily ice loss of around 200,000 or more per day at the moment, it is not significant.4. The ice shelves are frozen freshwater formed from glaciers moving into the ocean plus a few 10s of thousands of years of snowfall on top. I wonder if some have sea ice at their base from when they first formed?

Both NSIDC and JAXA use a mask to exclude the continent and the ice shelves from the measurements.

for me sea-ice is ice with water under it's kiel, kind of "swimming" in the water and if it's connected to land (makes contact to land) it's landfast sea-ice.

it's well possible that you're right but i opt for definition that are mutually understood and don't need a doctorate to be understood, else we shall never reach all 7 billion inhabitants on planet earth.

so for me, a berg, even should his origin be 1000km inland of greenland or antarctica, the moment it's swimming in the ocean it's sea-ice and "former" land-ice and perhaps in between "shelf-ice" and/or land-fast sea-ice.

Extent is 2nd lowest, though still at (a reducing) 0.85 million km2 greater than 2016 on this day, but 475 k below 2017. Extent loss from maximum is 972k (10.6%) greater than average so far, with on average 57.5% of extent loss for the season done and 61 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. Indeed, the average remaining melt from this day to minimum would produce a minimum of 1.24 million km2, 0.91 million km2 less than the record low in 2016-17. This result is hard to believe.

All models have limitations. The first table attached shows that remaining melt in two of the previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Most of the remaining ice is at low concentration, so being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Extent is 2nd lowest, though still at (a quickly reducing) 0.52 million km2 greater than 2016 on this day, but 598 k below 2017. Extent loss from maximum is 1.12 million km2 (11.7%) greater than average so far, with on average 60.3% of extent loss for the season done and 59 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. Indeed, the average remaining melt from this day to minimum would produce a minimum of 1.09 million km2, 1 million km2 less than the record low in 2016-17. This result is hard to believe.

All models have limitations. The first table attached shows that remaining melt in two of the previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Most of the remaining ice is at low concentration, adding to the chances of a record low extent. Being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Gerontocrat,Thanks, but the way, for adding other relevant single years to the decadal charts. Most helpful, indeed!

If I had only "liked" the post (or the first one with added single years), would the additional line be deemed appreciated? Or the trajectory? Or the size of the new daily drop? Or 'G. is just a cool person'? Or 'I'm cooling his heels because he has kompromat on me'?

Gerontocrat,Thanks, but the way, for adding other relevant single years to the decadal charts. Most helpful, indeed!

If I had only "liked" the post (or the first one with added single years), would the additional line be deemed appreciated? Or the trajectory? Or the size of the new daily drop? Or 'G. is just a cool person'? Or 'I'm cooling his heels because he has kompromat on me'?

That is for me to know and you to not to find out. A-ha.

First image shows how broken up the ice is compared with the same date in 2016, the year of record ice loss.

Extent is 2nd lowest, though still at (a quickly reducing) 377 k greater than 2016 on this day, but 755 k below 2017. Extent loss from maximum is 1.23 million km2 (12.6%) greater than average so far, with on average 61.6% of extent loss for the season done and 58 days to minimum (compared with last 10 years average).

A record low minimum is a real possibility, making 3 years in a row, and the first below 2 million km2. Indeed, the average remaining melt from this day to minimum would produce a minimum of 0.97 million km2, nearly 1.2 million km2 less than the record low in 2016-17. This result is hard to believe.

All models have limitations. The first table attached shows that remaining melt in two of the previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Most of the remaining ice is at low concentration, adding to the chances of a record low extent. Being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Extent is catching up to area as compaction percentage is climbing (see tealight's graph below).

Also looks like the temperature anomaly for 60-90S will be dropping over the next week (see GFS projections below).

Tealight's earlier point about the Weddell sea being very difficult to melt also suggests we are likely getting through the easier melt areas and might expect a slowdown soon (which is normal at this time of year according to the graphs).

Extent is 2nd lowest, though still (at a quickly reducing) 192 k greater than 2016 on this day, but 1 million km2 below 2017. Extent loss from maximum is 1.345 million km2 (13.1%) greater than average so far, with on average 64.7% of extent loss for the season done and 56 days to minimum (compared with last 10 years average).

The average remaining melt from this day to minimum would produce a minimum of 0.87 million km2, 1.28 million km2 less than the record low in 2016-17. A good proportion of the remaining ice is at low concentration, adding to the chances of a record low extent. However, when that is gone the solid land fast ice on the coast will likely slow down further melt to a crawl. Nevertheless, a record low minimum, the first below 2 million km2, is my guess for the 2019 minimum, continuing the loss of Antarctic sea ice over the last three years.

All models have limitations. The first table attached shows that remaining melt in three of the previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Extent is 2nd lowest, at a reducing 128 k greater than 2016 on this day, and 1,05 million km2 below 2017. Extent loss from maximum is 1.365 million km2 (13.0%) greater than average so far, with on average 65.9% of extent loss for the season done and 56 days to minimum (compared with last 10 years average).

The average remaining melt from this day to minimum would produce a minimum of 0.84 million km2, 1.31 million km2 less than the record low in 2016-17. A good proportion of the remaining ice is at low concentration compared with 2016 (see next post) adding to the chances of a record low extent. However, when that low concentration ice is gone the solid land fast ice on the coast will likely slow down further melt to a crawl. Nevertheless, a record low minimum, the first below 2 million km2, is my guess for the 2019 minimum, continuing the loss of Antarctic sea ice over the last three years.

All models have limitations. The first table attached shows that remaining melt in three of the previous years would result in an extent minimum of less than zero, an impossibility. Nevertheless, that is useful in that it shows how much extent this year is below that of the years to 2015.

Being in the Austral summer, low extent and area means with insolation high, albedo warming potential in the Antarctic is also high and well above average.

Not to be too contrary, but I think it is possible for a extent minimum of less than zero. There is ice on land, which could be said to be the source of the negative value for the extent minimum. If the land ice collapses like the side of Anuk... Of course, that's just playing with words really.

All models have limitations. The first table attached shows that remaining melt in three of the previous years would result in an extent minimum of less than zero, an impossibility.

I think models that generate negative sea ice over a given area might be predicting something useful, maybe important. The meaning of a negative ice thickness could be a statement that the surface waters to some depth (1m? 10m? 100?) are sufficiently warm to melt a thickness of ice equal to that value. Predictions of water warmth above freezing would have significance for the climate, weather, and future ice development.